Late Otiran and Early Aranuian Grassland in Central South Island

Pollen analysis suggests that in central South Island the late Otiran landscape on both sides of the Main Divide was dominated by grassland. An outstanding exception is the presence of Nothofagus menziesii forest at Blue Spur Road, Hokitika. The grassland persisted from about 26000 years to about 12000 years ago and during this time there was little variation in the character of the vegetation. During the period under review there were several well defined glacial advances and retreats and it is suggested that either the periods of time involved were too short to initiate vegetation change or that climate, for whatever reason, inhibited the development of shrubland. in any event the absence of change cannot be taken as evidence of an unchanging climate. The general character of the climate is discussed and it is concluded that a cold and stormy climate influenced the development of the vegetation. The west-east climatic gradient so characteristic of the trans-alpine environment was probably greater than it is today, a feature emphasised by the greater land area available because of the late-glacial lowering of sea-level.